User authentication is an important aspect of providing security for various computer systems, especially services for consumers on a publicly accessible computer system such as the Internet. Such services include, but are not limited to, electronic mail, remote storage, social networking applications and the like,
In addition to conventional user name and password combinations, some services include other authentication measures. For example, a sequence of secret questions and answers can be presented to the user. As another example, a device identifier, such as a serial number for the device itself, or for one or more components of the device, or other identifier such as a media access control (MAC) address, can be used to authenticate the user,
The location of the user also can be used to further verify or question the authenticity of the user. This location can be derived from computer network addresses, such as the internet protocol (IP) address used by the computer, from global position system (GPS) information and the like. For example, a system can maintain, for each user, a list of familiar locations from which the user is known to access the system. If the user attempts to access the system from an unfamiliar location, the user can be prompted for more information before the user is authenticated and access to the system is permitted.